This article was amended on Monday 5 September 2011 at 18.33. This article initially compared the average 13.6-month prison sentence handed to rioters convicted in the crown courts of theft or handling stolen property with the 4.1-month average custodial sentence issued across magistrates and crown courts in 2010. After publication, the Ministry of Justice has provided a more comparable average sentence for crown courts only, of 11.6 months. This represents a sentence 18% longer for rioters than typical crown court convictions, though this difference does not reflect the larger proportion of rioters sent to crown court nor the substantially higher custody rate for rioters.

Sentences in the crown court for theft or handling stolen goods in connection with last month's riots are more severe than the average for similar offences, a Guardian analysis shows.

A study of the early sentencing by crown court judges suggests they have replicated the punitive response of magistrates in response to the riots.

The average crown court sentence for individuals engaging in theft or handling stolen goods so far is 13.6 months, 18% more than the typical 11.6 month sentence handed down by crown courts for similar offences in 2010

The typical sentence for theft or handling stolen goods across all courts was 4.1 months – but many rioters face higher crown-court level sentences as a larger number of cases are passed upwards for tougher punishments. This category of offences is by far the largest in relation to the riots.

The data, part of a Guardian database covering more than 70% of the defendants processed through English courts for offences linked to the disorder, indicates that crown court judges have been even more willing to treat involvement in the riots as an aggravating factor than their counterparts in magistrates courts.

As well as surveys of those who took part in the disorder, the research will include interviews with residents, police and the judiciary, and an advanced analysis of more than 2.5m riot-related Twitter messages.

The project is based on a groundbreaking survey conducted in the aftermath of the Detroit riots in 1967 by the Detroit Free Press newspaper and Michigan's Institute for Social Research. The professor who led the Detroit study, Phil Meyer, is advising the research into the disturbances in England. LSE's involvement will be led by Professor Tim Newburn, head of the university's social policy department.

A month after the disturbances began in Tottenham, north London, the Guardian can also reveal:

• More than 90% of the cases being sentenced at crown court are resulting in jail terms, compared with an average rate for custodial sentences of 46%. Data previously released by the Ministry of Justice revealed that 44.6% of rioters sentenced at magistrate courts were sent to prison, almost four times the typical custody rate of 12.3%.

• A YouGov poll has found Britons have become more fearful since the rioting took place. The survey, which was commissioned by Nottingham University and compares attitudes before and after the riots, found people felt that their safety and wider society were under threat. Those polled were also more likely to express prejudiced views against minority groups, although they did not blame them for the disorder.

• An investigation into the Tottenham riots, which sparked copycat rioting across England, has found local police were alerted to rising tensions long before a protest over the killing of Mark Duggan by police descended into a riot. An email warning from a senior community adviser to police was sent to the borough commander 24 hours before the protest took place. She went on holiday the following day.

Magistrates courts have been delivering sentences about 25% longer than average, according to the Guardian data. The difference reflects the greater sentencing powers of crown courts, and potentially also the severity of riot-related cases transferred to the higher courts.

The most severe sentences relating to the riots were handed to Perry Sutcliffe-Keenan and Jordan Blackshaw, both from Chester, who received four years for inciting riots in their home towns of Warrington and Northwich on Facebook. None of the messages posted by either individual led to a riot. Both are appealing against their sentences.

The next most severe penalty was handed to 18-year-old Amed Pelle, given a 33-month prison term, also for posting Facebook messages. This was equal to the sentence passed on Dwaine Spence, who led a gang of 30 to 40 youths on a rampage through Wolverhampton town centre and hurled a 3ft plank of wood at a police car.

Other cases contained in the crown court data include Anderson Fernandes, 22, sentenced to 16 months for stealing ice cream, and 19-year-old Fabrice Bembo-Leta, who turned himself in to police after identifying himself from a published photo, and who was sentenced to 32 months in prison for burglary.

The shortest prison sentence issued so far to a riot-related offender in crown courts went to Steven Frear, 20, who received six weeks for possession of an offensive weapon.

The average sentence for the cases so far is 14.7 months. Many of the most serious cases, including charges of murder and attempted murder, are unlikely to be heard in court for several months. Only two of the 72 completed crown court cases to date resulted in non-custodial sentences.